This proposal seeks a renewal of funding for the United States based International Breast Cancer Study Group (IBCSG) Statistical and Data Management Center, a resource that contributes to International-US collaboration in the following areas: 1. Access to the IBCSG clinical database of 13,000 breast cancer patients enrolled in large-scale, randomized clinical trials with up to 21 years' maximum follow-up. 2. Access to the IBCSG tissue bank database for more than 1,000 patients with 10 years' median follow-up. 3. Expertise of statistical and medical investigators. 4. Collaboration in the development of the IBCSG research agenda. This resource gives NCI an opportunity to significantly improve their understanding of prognosis and treatment of women with operable breast cancer. The number of randomized trials that can be conducted in the United States cannot answer all of the questions about this population of patients. Support of this proposal for an IBCSG-NCI partnership will result in important new information about the appropriate clinical use of combined chemoendocrine therapy, timing and duration of adjuvant chemotherapy, endocrine therapies, management strategies for the axilla, and high dose chemotherapy. The long-range goal of the IBCSG is to find the best possible treatments for operable breast cancer. The specific aims of this application comprise the major areas of research toward this goal. 1. To provide US-based statistical and data management collaboration for the design, conduct, analysis, and reporting of IBCSG randomized clinical trials evaluating adjuvant therapies. 2. To facilitate correlative research by providing access to their uniformly treated and followed populations of patients with tissue collection at diagnosis. 3. To facilitate collaboration on database studies to identify and confirm the relationship between characteristics of breast cancer patients and/or tumors and response to adjuvant therapies. 4. To enhance collaboration between the IBCSG and US cooperative groups in the area of quality-of-life evaluation for patients with breast cancer.